1. Field of the Invention
The present invention relates to tobacco drying processes and more particularly to a process for forming favorable flavor compounds in a tobacco with an ammonia source while drying the tobacco at controlled pressures.
2. Description of the Prior Art
It is generally well known in the tobacco treating art to use alkali and steam to remove nicotine from tobacco. Long since expired U.S. Pat. No. 896,124 issued to G. B. Lindenberger, et al., on Aug. 18, 1908, teaches applying caustic soda to tobacco stems or stalks and passing steam successively through flow through chambers containing the tobacco at temperatures of 250.degree. F. to 300.degree. F. to extract nicotine and other volatile constituents from the tobacco. Long expired U.S. Pat. No. 246,975, issued to C. S. Phillips on Sept. 13, 1881 teaches utilizing ammonia gas to eliminate tobacco odors and U.S. Pat. No. 999,674, issued to J. Sartig on Aug. 1, 1911, teaches treating tobacco with ammonia for liberating nicotine and then passing steam below 212.degree. F. continuously through the tobacco to carry off nicotine with the steam. U.S. Pat. No. 1,168,029, issued to J. K. Probst on Jan. 11, 1916, teaches treating cured tobacco with ammonia vapors at temperatures of 80.degree. F. to 120.degree. F. and U.S. Pat. No., 1,671,259, issued to T. Schloesing on May 28, 1928, teaches circulating a mixture of steam and ammonia through tobacco at temperatures below 212.degree. F. to remove nicotine at temperatures below 212.degree. F. U.S. Pat. No. 1,880,336, issued to A. Wenusch on Oct. 4, 1932, teaches passing heated air through tobacco until the tobacco reaches 212.degree. F. and then passing superheated steam therethrough to reduce the nicotine in the tobacco. U.S. Pat. No. 1,984,445, issued to W. Wagner on Dec. 18, 1934, teaches removing nicotine from tobacco by passing an ammonia vapor through the tobacco, aerating the tobacco and then exposing the tobacco to acetic acid while subjecting the tobacco to an evaporation heat. U.S. Pat. No. 2,136,485, issued to F. Berka, et al., on Nov. 15, 1983, teaches denicotizing tobacco by passing a mixture of air and ammonia therethrough at temperatures below 212.degree. F. U.S. Pat. No. 4,153,063, issued to W. Roselius et al., on May 8, 1979, teaches denicotizing tobacco by passing carbon dioxide therethrough at very high pressure ranges and temperatures below 212.degree. F.
A number of other patents, such as U.S. Pat. Nos. 3,151,118, issued to G. P. Moser on Sept. 29, 1964; 3,742,962, issued to C. Brochot on July 3, 1973, and 3,821,960, issued to L. Egri on July 2, 1974, teach or suggest the broad use of an ammonia source and steam at comparatively low temperature ranges below 250.degree. F. for the purpose of denicotizing tobacco. Further, U.S. Pat. No. 3,760,815 issued to E. J. Deszyck on Sept. 25, 1973, teaches the use of an ammonia source and salts for the purpose of tobacco coherence. In addition, U.S. Pat. Nos. 3,771,533, issued to R. G. Armstrong et al., on Nov. 17, 1973; 4,248,252, issued to A. T. Lendvay et al., on Feb. 3, 1981; 4,266,562, issued to H. B. Merritt et al., on May 12, 1981, all suggest use of an ammonia source and CO.sub.2, some even at temperatures in excess of 250.degree. F., for purposes of puffing or expanding tobacco. In fact, flavor has been a consideration in utilizing an ammonia source for flavor enhancement of a synthetic material in U.S. Pat. Nos. 4,079,742 issued to N. B. Rainer et al., on March 21, 1978, and 4,184,495 issued to N. B. Rainer et al., on Jan. 22, 1980, and in utilizing an ammonia source with a carboxylic acid as taught by U.S. Pat. No. 4,286,606, issued to J. W. Swain et al., on Sept. 1, 1981. Other U.S. patents noted and being concerned with enhancing flavor through nitrogen, amino acid or ammonia treatment of tobacco have been U.S. Pat. Nos. 4,150,677; 4,306,577; and 4,379,464 respectively.
It is futher known to dry tobacco at high temperatures, the tobacco having initial moisture content usually above 16% and in the food processing art to entrain food in a heated gas stream to heat and discharge the food in a lower pressure zone. For example, U.S. Pat. No. 3,357,436, issued to A. H. Wright on Dec. 12, 1967, teaches improving tobacco fill value by drying at a temperature range between 250.degree. F. to 600.degree. F. and controlling moisture content of the tobacco to be dryed between 16 and 35% to provide dryed tobacco of between 9% and 23% moisture content. U.S. Pat. No. 3,661,071 and its divisional No. 3,754,930, both issued to R. Toei et al., on May 9, 1972, and Aug. 28, 1973, respectively, teach the drying of food stuffs in a pressurized heated gas stream and discharging the same to a zone of lower pressure. Further, U.S. Pat. No. 3,734,104, issued to W. Buchanan et al., on May 22, 1973, teaches rapidly heating and expanding moisturized tobacco for brief time periods of less than three seconds at temperatures as high as 750.degree. F. to increase tobacco fill value and U.S. Pat. No. 4,167,191, issued to J. Jewell et al., on Sept. 11, 1979, teaches drying expanded tobacco by heating tobacco in steam and air at temperatures of 250.degree. F. to 650.degree. F. in the presence of an absolute humidity at a level above that which produces a wet-bulb temperature of at least 150.degree. F. Moreover, two patents to B. Hedstrom, namely U.S. Pat. Nos. 3,808,093, issued on Apr. 30, 1974, and 4,043,049, issued on Aug. 23, 1977, as well as Canadian Pat. No. 879,811, issued on Aug. 31, 1971, teach drying of wood pulp in particulate form in entraining steam at elevated pressure, the steam heating and carrying the particulate pulp through the process. These aforenoted processes when involving tobacco have recognized the desirability of improving smoking quality and filling power but have either operated at atmospheric pressure when tobacco has been involved or, when operating under pressure, have involved food stuffs and wood pulps, requiring extensive and complex equipment in consideration of the product to be treated. Further, past tobacco treating processes utilizing an ammonia source and steam, have employed continuous flow through systems to extract nicotine from the treated tobacco or to expand the tobacco; or the past art has utilized an ammonia source and a specifically selected organic synthetic compound when flavor has been a consideration.
In accordance with the present invention, an improved, straightforward, efficient and economical tobacco drying process is provided which recognizes the advantages and benefits of drying tobacco at high temperatures and increased pressures and utilizing an ammonia source with the tobacco to be treated. The present invention further provides a process which, at the same time, avoids past required extensive, complex and expensive equipment costs involved in high temperature and pressure operations, obtaining and improved tobacco product for smoking articles, such as cigarettes, which has smoother and more flavorable smoking qualities with lower impact and irritation properties, lower nicotine and alkaloid ingredients and increased fill values.
Various other features of the present invention will become obvious to one skilled in the art upon reading the novel disclosure set forth herein.